1.5 The Theory of Plate Tectonics


Vocabulary


Plates: the separate sections of the lithosphere
Scientific Theory: a well tested concept that explains a wide range of observations
Plate Tectonics: the geological theory that states that the Earth's plates are constantly in motion
Faults: breaks in the Earth's crust where rocks have slipped past each other
Transform Boundary: a place where two plates slip past each other, moving in opposite directions
Divergent Boundary: the place where two plates move apart
Rift Valley: a deep valley which forms along divergent boundaries
Convergent Boundary: the place where two plates come together

A Theory of Plate Motion

  • Plate tectonics

    • Driven by convection currents in the mantle
      • Convection currents rise in the asthenosphere and spread out in the lithosphere

Plate Boundaries

  • Transform Boundaries

    • Earthquakes occur frequently along these boundaries
  • Divergent Boundaries

    • Occur along the mid-ocean ridge
    • Also occur on land
      • Rift valleys occur near divergent boundaries
  • Convergent Boundaries

    • When 2 plates converge, they cause collisions, subduction occurs and mountain ranges form.
      • Oceanic crust and oceanic crust( subduction occurs)
      • Continental crust and oceanic crust( collisions happen)
      • Continental crust and continental crust( mountain ranges form)
    • Density determines which plate comes on top
    • Can create mountain ranges